Although many investigations have been conducted to characterize the pathogenesis of interstitial lung diseases (ILDs), few have examined the epidemiology of these disorders in a general population. To address current research needs related to the epidemiology of ILDs, in 1988 a population-based registry of patients with ILDs was begun in Bernalillo County, New Mexico, funded by a FIRST Award from the NHLBI. The purpose of this competing continuation application is to continue and complete the work conducted from 1988 through 1992, with the following specific aims: 1) to complete case-ascertainment, data collection, and follow-up of incident cases of ILD identified during the period 10/1/88-9/30/92; 2) to describe the incidence of ILDs; 3) to describe the clinical characteristics of patients with ILDs; and 4) to describe prognosis of the most common ILDs. Sources of information for identifying incident cases include pulmonary and primary care physicians, hospital discharge diagnoses, histopathology reports, and death certificates. Regular screening of these sources is conducted, and as of 10/1/92 330 incident cases have been identified. Continued funding will permit complete ascertainment of 400 to 450 cases. After a case of ILD is identified, standardized data are collected from the patient's medical record and an interviewer administered questionnaire. In addition a blood specimen is obtained for assay of serum precipitins, and chest roentgenograms and histopathology specimens are reinterpreted. Follow-up procedures include an abstract of the medical record and a brief telephone interview. The major prognostic outcome will be survival, and predictors of survival will be examined with proportional hazards models.